Note: Descriptions are shown in the official language in which they were submitted.
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WO 99/56929 PCT/US98/08804
MULTIAXIS ROTATIONAL MOLDING
METHOD AND APPARATUS
This invention relates to a novel molding method and
apparatus and more particularly relates to a new multiaxis
rotational molding method and apparatus.
The production of man-made plastic and resin articles is an
industry that utilizes a high degree of automatically controlled
continuous processing. However, for units of appreciable size,
batch processing still is the rule rather than the exception. For
example, in the production of fiberglass structures such as boats,
it is customary to construct the hulls by hand. A plurality of
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resin and fiberglass layers are sequentially laminated on an open
mold or a plurality of mixed resin/chopped fiber coatings are
applied over the mold.
Such hand building procedures require a great amount of
labor, supervision and continuous inspection to insure that a
reasonable level of quality is achieved. This greatly increases
the cost of the product.
The applicant's earlier patents listed above provide a novel
method and apparatus for producing both large and small molded
structures continuously. The apparatus includes unique
combinations of components to.produce.a wide variety of different
products. Achieving this capability requires a major capital
investment. Also, personnel to utilize the broad parameters of
the apparatus normally are highly trained and experienced.
The present invention provides a novel molding method and
apparatus which not only overcome the deficiencies of present
technology but also provide features and advantages not found in
earlier expedients. The multiaxis rotational molding method and
apparatus of the invention provide a means for the production of
a large number of uniform high quality products rapidly and
efficiently.
The multiaxis rotational molding apparatus of the present
invention is simple in design and can be produced relatively
inexpensively. Commercially available materials and components
can be utilized in the manufacture of the apparatus. Conventional
metal fabricating procedures can be employed by semi-skilled labor
in the manufacture of the apparatus. The apparatus is durable in
construction and has a long useful life with a minimum of
maintenance.
The apparatus of the invention can be operated by individuals
with limited mechanical skills and experience. A Large number of
high quality molded structures can be produced rapidly by such
persons safely and efficiently with a minimum of supervision.
The molding method and apparatus of the invention can be
modified to mold a wide variety of new structures. Variations
both in product configuration and composition can be attained
simply and conveniently with the method and apparatus of the
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invention. Even with such variations, uniformity and quality of
product dimensions and shapes still are maintained without
difficulty.
A novel method of the present invention for continuously
forming integrally molded structures includes the steps of
rotating a plurality of independently movable multisection mold
assemblies about a plurality of axes. A first freshly formed
polymerizable mixture is supplied to a first mold assembly. The
first polymerizable mixture is flowed over surfaces of a first
enclosed mold cavity within the first mold assembly while
selectively heating at least one of the mold sections of the first
mold assembly in a preselected heating profile. The flowing of
the first mixture over the first mold cavity surfaces, the heating
of the mold section and the formation of a first resin therefrom
are monitored.
The first polymerizable mixture is supplied to a second mold
assembly. The first polymerizable mixture is flowed over surfaces
of a second enclosed mold cavity within the second mold assembly
while selectively heating at least one of the mold sections of the
second mold assembly in a preselected heating profile.
Simultaneously therewith, a freshly formed second polymerizable
mixture is supplied to the first mold assembly. The second
polymerizable mixture is flowed over the first resin within the
first mold cavity while selectively heating at least one of the
mold sections of the first mold assembly in a preselected heating
profile. The flowing of the first and second polymerizable
mixtures within the first and second mold cavities, the heating
of the mold sections and the formation of first and second resins
therefrom are monitored.
The first polymerizable mixture is supplied to a third mold
assembly. The first polymerizable mixture is flowed over surfaces
of a third enclosed mold cavity within the third mold assembly
while selectively heating at least one of the mold sections of the
third mold assembly in a preselected heating profile.
Simultaneously therewith, the second polymerizable mixture is
supplied to the second mold assembly. The second polymerizable
mixture is flowed over the first resin within the second mold
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assembly while selectively heating at least one of the mold
sections of the second mold assembly in a preselected heating
profile. The flowing of the first and second polymerizable
mixtures within the second and third mold cavities, the heating
of the mold sections and the formation of first and second resins
therefrom are monitored.
The supplying of the first and second polymerizable mixtures
succeeding mold assemblies and the flowing of the mixtures into
the respective mold cavities while selectively heating the mold
sections is continued until all of the mold assemblies have
received the mixtures. Also the monitoring of the flowing of the
mixtures, the heating of the mold sections and the formation of
resins therefrom are continued.
The rotation of the mold assemblies is continued throughout
the steps of the continuous molding operation while monitoring
individually each axis rotation of the mold assemblies. The
monitored flowing of each mixture, the monitored heating of the
mold sections and the monitored formation of each resin are
coordinated with each monitored axis rotation in a preselected
profile to form the integrally molded structures of the first and
second resins.
The mold sections of each mold assembly are separated after
the integrally molded structure therein has achieved structural
integrity within the mold cavity. The structure is removed from
the separated mold sections and the steps are repeated to form a
multiplicity of the integrally molded structures on a continuing
basis. Advantageously, the integrally molded structures are
separated from the mold assembly by cooling the molded sections.
The method of the invention preferably includes the steps of
flowing at least one of the polymerizable mixtures into a mold
cavity and rotating the cavity only a sufficient amount to coat
the first mold section before heating the coated mold section to
set the coating in place. Thereafter, the rotation of the mold
cavity is continued to coat an adjacent second mold section
followed by the heating of the second coated section to set the
coating adhering thereto. Further rotation coats each succeeding
mold section and the heating thereof results in the formation of
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an integrally molded product within the mold cavity. Subsequent
cooling of the mold sections frees the molded structure from the
mold assembly.
Advantageously, the mold assembly is transferred to an
adjacent mold receiving station prior to separating the mold
sections and removing the molded structure. Thereafter, the mold
assembly is returned to a molding position for repeating the
method of the invention. A plurality of mold assemblies may be
provided for each molding position so molding can continue while
IO other mold assemblies are being opened and being prepared for
another molding cycle.
If desired, solid particles may be introduced into the mold
cavity of each mold assembly and the particles distributed in a
preselected configuration before supplying the first polymerizable
mixture to the respective mold assembly. Also, micro spheres may
be introduced into at least one of the polymerizable mixtures
prior to molding.
Benefits and advantages of the novel multiaxis rotatable
molding method and apparatus of the present invention will be
apparent from the following description and the accompanying
drawings in which:
Figure 1 is a side view of one form of multiaxis rotational
molding apparatus of the invention;
Figure 2 is a fragmentary top view of the molding apparatus
shown in Figure 1;
Figure 3 is an enlarged fragmentary side view of a molding
portion of the molding apparatus shown in Figures 1 and 2;
Figures 4 - 11 are schematic illustrations of steps in the
molding method of the present invention;
Figure 12 is a side view of a further form of the multiaxis
rotational molding apparatus of the present invention;
Figure 13 is a side view taken from the left of the molding
apparatus shown in Figure 12;
Figure 14 is a fragmentary side view of another form of
multiaxis rotational molding apparatus of the invention; and
Figure 15 is a fragmentary top view of a rotational drive
portion of the molding apparatus shown in Figure 14.
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As shown in Figures 1-3 of the drawings, one form of
multiaxis rotational molding apparatus 11 of the present invention
includes a support portion 12, a molding portion 13 and a control
portion 14.
The support portion 12 of the multiaxis rotational molding
apparatus 11 of the invention includes a plurality of arm members
17,18,19,20 disposed in a generally horizontal orientation. One
end 21 of each arm member 17-20 extends from an upstanding frame
section 22. Advantageously, the upstanding frame section 22
includes a central upstanding section 23 from which the arm
members extend radially as shown in the drawings.
The molding portion 13 of the rotational molding apparatus
11 includes a plurality of mold supporting assemblies 26. One
mold supporting assembly is rotatably mounted adjacent a free end
24 of each arm member 17-20. Each mold supporting assembly 26
includes an independently rotatable mold connector section 2'~.
As shown in the drawings, the molding apparatus preferably
includes mold assembly receiving stations 28 adjacent each arm
member 17-20. The mold receiving stations advantageously also
include mold transferring means such as hoist 29.
The molding portion 13 further includes a plurality of mold
assemblies 30,31,32,33. As shown in Figures 4 - 11 each mold
assembly includes a plurality of separable mold sections
35,36,37,38 forming a substantially enclosed mold cavity 39. A
heating element is associated with each mold sections 35-38. For
example, mold section 35 includes heating element 41; section 36,
heating element 42; section 37, element 43 and section 38, element
44:
The heating elements 41-44 advantageously include
thermoelectric elements. Preferably, the thermoelectric elements
function in an operating temperature range providing heating and
cooling as will be described hereinafter.
Connecting means e.g. electromagnets 46 located in flange
sections 47 of the mold sections (Figure 3), selectively secure
the assembled mold sectionstogether. Also, connecting means 48
secure the assembled mold assembly to mold connector section 27.
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The control portion 14 of the molding apparatus 11 of the
present invention includes actuating means including drive means
50,51 for each mold assembly. One drive means 50 rotates each
mold supporting assembly 26 and the mold assembly 30-33 affixed
thereto. Another drive means 51 rotates each mold supporting
assembly 26 and the mold assembly affixed thereto along an axis
generally perpendicular to the axis of rotation achieved with
drive means 50. Other drive means may be provided for opening,
closing, transferring mold assemblies, etc. as required.
I0 The control portion 14 also includes programmable memory
means 57, coordinating means 58, monitoring means 59 and circuitry
therefor. The drive means 50,51 advantageously include gear
motors, chains and sprockets connected thereto. Preferably, the
gear motors are variable speed motors. The actuating means may
activate other components such as pumps, valves, drives,
electromagnets, etc.
The coordinating means 58 advantageously includes a process
controller 60 that initiates changes in the flows of materials and
speeds of drives for each mold assembly to bring variations
therein back to the respective rates specified in the programs
present in the memory 57. This coordination commonly is achieved
through the transmission of information such as digital pulses
from the monitors and/or sensors at the control components to the
process controller 60.
The operating information is compared with the preselected
programming parameters stored in the memory 57. If differences
are detected, instructions from the controller change the
operation of the components to restore the various operations to
the preselected processing specifications.
In the use of the multiaxis rotational molding apparatus 1i
of the present invention, the designs of the structures desired
first are established. Then, each design is programmed into the
memory 57.
To start the operation of the apparatus 11, buttons and/or
switches of a control panel (not shown) are depressed to activate
the memory 57 and the other components of the control portion 14.
The coordinating means 58 energizes drive means 50,51.
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Also, monitors 59 and pumps, valves, etc. (not shown) are
energized by the coordinating means 58 in the preselected
sequences of the program stored in the memory 57. This causes the
raw materials in reservoirs (not shown) to advance along inlet
conduits toward the respective mold assemblies 30-33. For
example, to mold a structure including a polyurethane resin, one
reservoir may contain a liquid reactive resin forming material,
a second reservoir a particulate solid recyclable material and a
third or more reservoirs - colors, catalysts, etc. as required.
To produce high quality molded structures of the invention,
it is important that the raw material be uniform in volume and
composition. This can be facilitated by providing a continuous
flow of raw materials and/or mixtures thereof onto the cavity
surface of a mold assembly 30-33. However, the volume of the
mixture delivered will vary depending upon the particular
incremental area being covered at any instant. Also, the delivery
to a particular mold assembly will be terminated completely when
a molded structure is being removed from that assembly.
Advantageously, a separate bypass conduit (not shown) is
utilized from the end of each inlet conduit at a point adjacent
a particular mold assembly back to the respective reservoir. This
construction provides for the delivery of uniform raw materials
and/or freshly formed mixtures thereof even though the distance
is considerable between the reservoirs and the mold assemblies.
The control portion 14 coordinates the operation of the various
system components so the required formulation flows onto the
desired areas of a particular preselected mold cavity.
Rotation of each mold assembly 30-33 about an axis concentric
with that of mold connector section 27 and rotational movement of
the mold assembly about a second axis perpendicular to its
concentric axis are started and continue while the raw materials
and/or freshly formed polymerizable mixtures are transferred into
each preselected cavity 39 of a mold assembly. The multiple axis
rotational movement and any arcuate movement are continued to
complete the flow of the mixture over all areas being covered
within a particular mold cavity. All movements are controlled
within the parameters stored in the memory 57.
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For particular structures, the movements about the respective
axes may be continuous and/or intermittent at changing rates.
Also, it may be desirable to provide arcuate rotation, that is,
movement about an arc such as a rocking motion. Monitors 59
located within each mold assembly 30-33 signal the process
controller 60 when each polymerizable mixture has been distributed
over the preselected areas of the respective mold cavity so the
controller can initiate the next step of the molding method.
With the control components of the molding apparatus 11
activated, a first dispenser 53 is aligned with the first mold
assembly 30. As schematically illustrated in Figures 4 - 11, a
first freshly formed polymerizable mixture is introduced into mold
cavity 39 and flows downwardly by gravity onto the cavity surface
of mold section 35 disposed at the bottom of the cavity.
Thereafter, the mold assembly 30 is rotated to a position
shown in Figure 5 wherein a coating 63 is forming on the cavity
from the pool of liquid 62 remaining in the mold bottom.
Simultaneously with the rotation, heating element ~1 of mold
section 35 is energized to raise the temperature of the cavity
surface and set the coating to form a resin layer thereof (Figures
5,6).
As the rotation of the mold assembly 30 continues a coating
forms on mold section 36 emerging from the liquid pool therein
(Figures 7,8). Heating element ~2 is energized, heating mold
section 36 setting the coating and forming the resin layer in
place. Further rotation of the mold assembly forms resin layers
. over the surfaces of mold sections 37,38 with the heating and
setting of each coating as shown in Figures 9,10.
When all of the mold sections have been coated, heated and
set and the structure being molded is complete, the heating
elements 41-44 are de-energized causing the mold sections to cool
and contract away from the integrally molded structure 64. This
allows the structure to be separated from the mold assembly so
that the molding operation can be repeated. The flowing of the
polymerizable mixture over the cavity surfaces, the heating of the
respective mold sections and the formation of a resin structure
therefrom all are monitored during the molding operation.
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To form multilayer structures, the steps described above may
be repeated and before the mold assembly is opened, a second
freshly polymerizable mixture is introduced into the resin coated
mold cavity and the steps repeated with the second mixture. The
coatings formed on the cavity surfaces are set in place by heating
the mold sections sequentially forming a double walled structure.
With the appropriate selection of the formulation of the mixtures,
the resulting molded structure, for example, may provide an
integrally laminated two layer structure with a durable outer
surface and a chemical resistant lining.
Continuous production of. such structures can be achieved by
aligning the first polymerizable mixture with an adjacent second
mold assembly 31 and flowing the polymerizable mixture into the
second mold cavity thereof. Simultaneously therewith, a second
polymerizable mixture may be aligned with the first mold assembly
30 and the mixture delivered into the mold cavity of the first
mold assembly 30 flowing over the first resin formed in the
cavity. The flowing of the first and second mixtures within the
first and second mold cavities, the heating and setting of the
coatings and the formation of a first and second resin therefrom
are monitored.
Thereafter, the first polymerizable mixture can be aligned
with a third mold cavity of an adj acent third mold assembly 3Z and
the first mixture flowed over the cavity surfaces as described
above. Simultaneously therewith, the second mixture is aligned
with the second mold cavity of the second mold assembly 31 and the
second mixture flowed over the first resin formed therein. The
flowing of the first and second resins and formation of first and
second resins therefrom are monitored.
The flowing of the first and second polymerizable mixtures
into each mold cavity of any additional mold assemblies is
continued until all of the mold assemblies have received the
mixtures according to the preselected molding parameters. The
monitoring of the mixture flow, the heating of the mold sections
sequentially, the formation of resins therefrom and mold assembly
rotation are continued throughout the molding operation as well
as the coordinating of this operating information with the
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preselected program profile.
When a molded structure within a mold cavity is sufficiently
cured that it possesses structural integrity, rotation of the
respective mold assembly is stopped and the mold assembly is
transferred to an adjacent mold receiving station 28 with hoist
means 29. The mold sections 35-38 are separated by cooling them
to free the structural unit.
The molded structure then may be set aside to complete the
curing of the resin therein. During this period, the molded
structure, free of the mold's restraint, stresses the high density
outer skin or layer. This stressing of the skin increases the
strength and puncture resistance thereof and also the structural
strength of the unit itself.
The mold sections 35-38 are prepared for another molding
cycle. This may include changing the position of one or more mold
sections with respect to each other, the substitution of mold
sections with different configurations and the like. Also, cavity
changing inserts may be employed, if desired.
The mold sections then are assembled together and secured
such as by energizing electromagnets 46. The mold assembly now
is ready for repositioning on the adjacent arm member when the
next mold assembly is removed therefrom.
Figures 12 and 13 illustrate another form of rotational
molding apparatus 70 of the present invention. The apparatus
provides for the molding of large structures on cantilever multi
axis molding apparatus without major reconstruction thereof.
The rotational molding apparatus 70 as shown in the drawings
includes a support portion 71 and a molding portion 72. The
support portion includes a vertical frame section 73 with a
horizontally oriented arm member 74 extending therefrom. A U-
shaped mold supporting assembly 76 is rotatably mounted on arm
member 74 through a shaft 77.
A vertically disposed arcuate guide member 78 is mounted on
frame section 73 in the path of one leg 79 of U-shaped mold
supporting assembly 76. Drive means shown as motor 80 operatively
connects the mold supporting assembly 76 with guide member 78 and
advances there along to rotate the supporting assembly about shaft
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77 as an axis. A mold assembly 81 is rotatably supported between
the legs 79,82 of the supporting assembly 76. The mold assembly
is rotated about an axis perpendicular to shaft 77 by drive means
83 mounted on leg 82.
Figures 14 and 15 illustrate a further form of multiaxis
rotational molding apparatus of the invention. Molding apparatus
84 includes a support portion 85 and a molding portion 86. The
support portion 85 includes a plurality of drive wheel assemblies
87,88 selectively movable from a base surface 89 in a preselected
drive profile. The drive wheel assemblies preferably are arranged
in pairs and advantageously are pivotable about an axis
perpendicular to the base surface.
The support portion also may include a frame section 90 shown
as a generally spherical configuration with a plurality of pairs
of parallel endless tracks 91 arranged in a perpendicular
orientation to other pairs of tracks 92. A mold assembly 93 is
mounted within frame section 90 along a central axis thereof. The
tracks 91,92 preferably are recesses engageable with the drive
wheel assemblies.
Structures may be formed with the molding apparatus 84 of the
invention continuously and automatically employing the control
portion 14 of molding apparatus 11 described above. The control
portion is programmed to selectively engage preselected drive
wheel assembllies with the endless tracks 91, 92 of spherical frame
section 90. Rotation of the drive wheels in a preselected
rotational profile rotates a mold assembly 93 supported thereby
along a plurality of axes in the same way as described above with
molding apparatus 11 and 70. In addition, the control portion can
be programmed to transfer a mold assembly from one pair of drive
wheel assemblies to an adjacent pair and onto the next pair. In
this way, the programmed memory not only can distribute a
polymerizable mixture over a mold cavity, but also it can transfer
a mold assembly from one molding station to another.
The polymerizable mixtures employed to produce the structures
of the invention are selected to be capable of reaction to form
the particular resin desired in the final structure.
Advantageously, the resin is a thermosetting resin such as
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a polyurethane or polyester. Should a polyurethane be desired,
one component may be an isocyanate and another may be a polyol.
More commonly, different partially formed materials which upon
mixing interact to form the desired polyurethane may be employed.
Examples of such partially formed materials include so-called "A
stage" resins and "B stage" resins.
Other resin forming systems may utilize a resin forming
material and a catalyst. Additional components can be pre-mixed
with one of the resin formers, e.g. fillers, reinforcements,
colors and the like.
The particulate solid additive material may be any of a wide
variety of materials which impart special properties to the final
structure such as wear resistance, lubricity, electrical,
magnetic, temperature conductivity ox isolation, and the like.
Some inexpensive particulate materials generally are readily
available at a particular job site. Natural mineral particulate
material such as sand and gravel normally axe present or can be
produced simply by crushing rock at the site.
Waste or recycled materials which can be shredded or ground
into particles of suitable size can be utilized. Particularly
useful are particles formed by shredding or grinding discarded
tires and similar products. Since the particles are encapsulated
with the resin forming material and not saturated therewith, many
different waste materials may be employed.
The above description and the accompanying drawings show that
the present invention provides a novel multiaxis rotational
molding method and apparatus which not only overcome the
deficiencies and shortcomings of earlier expedients, but in
addition provide novel features and advantages not found
previously. The method and apparatus of the invention provide
simple inexpensive means for producing uniform high quality
products efficiently and at high rates of production.
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The apparatus of the invention is efficient in its design
and operation and is relatively inexpensive. Commercially
available materials and components can be utilized in the
fabrication of the apparatus using conventional metal working
techniques and procedures.
Structures can be produced automatically with the apparatus
of the invention by operators with limited experience and
aptitude after a short period of instruction. The apparatus is
durable in construction and has a long useful life with a minimum
of maintenance.
The method and apparatus.of the invention can be utilized to
mold a wide variety of different products. Variations in
structure, configuration and composition of the products can be
achieved simply and quickly with the method and apparatus of the
invention.
It will be apparent that various modifications can be made
in the multiaxis rotational molding method and apparatus described
in detail above and shown in the drawings within the scope of the
present invention. The size, configuration and arrangement of
components can be changed to meet specific requirements. For
example, the mold assemblies may be arranged differently with
respect to one another. In addition, the number and sequence of
processing steps may be different. Also, the apparatus may
include other drive and actuating components and mechanisms.
These and other changes can be made in the method and
apparatus described provided the functioning and operation thereof
are not adversely affected. Therefore, the scope of the present
invention is to be limited only by the following claims.
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